//
// This file is a part of UERANSIM open source project.
// Copyright (c) 2021 ALİ GÜNGÖR.
//
// The software and all associated files are licensed under GPL-3.0
// and subject to the terms and conditions defined in LICENSE file.
//

#include "zuc.hpp"

static thread_local uint32_t LFSR_S[16];

static thread_local uint32_t F_R1;
static thread_local uint32_t F_R2;

static thread_local uint32_t BRC_X[4];

static thread_local uint8_t S0[256] = {
    0x3e, 0x72, 0x5b, 0x47, 0xca, 0xe0, 0x00, 0x33, 0x04, 0xd1, 0x54, 0x98, 0x09, 0xb9, 0x6d, 0xcb, 0x7b, 0x1b, 0xf9,
    0x32, 0xaf, 0x9d, 0x6a, 0xa5, 0xb8, 0x2d, 0xfc, 0x1d, 0x08, 0x53, 0x03, 0x90, 0x4d, 0x4e, 0x84, 0x99, 0xe4, 0xce,
    0xd9, 0x91, 0xdd, 0xb6, 0x85, 0x48, 0x8b, 0x29, 0x6e, 0xac, 0xcd, 0xc1, 0xf8, 0x1e, 0x73, 0x43, 0x69, 0xc6, 0xb5,
    0xbd, 0xfd, 0x39, 0x63, 0x20, 0xd4, 0x38, 0x76, 0x7d, 0xb2, 0xa7, 0xcf, 0xed, 0x57, 0xc5, 0xf3, 0x2c, 0xbb, 0x14,
    0x21, 0x06, 0x55, 0x9b, 0xe3, 0xef, 0x5e, 0x31, 0x4f, 0x7f, 0x5a, 0xa4, 0x0d, 0x82, 0x51, 0x49, 0x5f, 0xba, 0x58,
    0x1c, 0x4a, 0x16, 0xd5, 0x17, 0xa8, 0x92, 0x24, 0x1f, 0x8c, 0xff, 0xd8, 0xae, 0x2e, 0x01, 0xd3, 0xad, 0x3b, 0x4b,
    0xda, 0x46, 0xeb, 0xc9, 0xde, 0x9a, 0x8f, 0x87, 0xd7, 0x3a, 0x80, 0x6f, 0x2f, 0xc8, 0xb1, 0xb4, 0x37, 0xf7, 0x0a,
    0x22, 0x13, 0x28, 0x7c, 0xcc, 0x3c, 0x89, 0xc7, 0xc3, 0x96, 0x56, 0x07, 0xbf, 0x7e, 0xf0, 0x0b, 0x2b, 0x97, 0x52,
    0x35, 0x41, 0x79, 0x61, 0xa6, 0x4c, 0x10, 0xfe, 0xbc, 0x26, 0x95, 0x88, 0x8a, 0xb0, 0xa3, 0xfb, 0xc0, 0x18, 0x94,
    0xf2, 0xe1, 0xe5, 0xe9, 0x5d, 0xd0, 0xdc, 0x11, 0x66, 0x64, 0x5c, 0xec, 0x59, 0x42, 0x75, 0x12, 0xf5, 0x74, 0x9c,
    0xaa, 0x23, 0x0e, 0x86, 0xab, 0xbe, 0x2a, 0x02, 0xe7, 0x67, 0xe6, 0x44, 0xa2, 0x6c, 0xc2, 0x93, 0x9f, 0xf1, 0xf6,
    0xfa, 0x36, 0xd2, 0x50, 0x68, 0x9e, 0x62, 0x71, 0x15, 0x3d, 0xd6, 0x40, 0xc4, 0xe2, 0x0f, 0x8e, 0x83, 0x77, 0x6b,
    0x25, 0x05, 0x3f, 0x0c, 0x30, 0xea, 0x70, 0xb7, 0xa1, 0xe8, 0xa9, 0x65, 0x8d, 0x27, 0x1a, 0xdb, 0x81, 0xb3, 0xa0,
    0xf4, 0x45, 0x7a, 0x19, 0xdf, 0xee, 0x78, 0x34, 0x60};

static thread_local uint8_t S1[256] = {
    0x55, 0xc2, 0x63, 0x71, 0x3b, 0xc8, 0x47, 0x86, 0x9f, 0x3c, 0xda, 0x5b, 0x29, 0xaa, 0xfd, 0x77, 0x8c, 0xc5, 0x94,
    0x0c, 0xa6, 0x1a, 0x13, 0x00, 0xe3, 0xa8, 0x16, 0x72, 0x40, 0xf9, 0xf8, 0x42, 0x44, 0x26, 0x68, 0x96, 0x81, 0xd9,
    0x45, 0x3e, 0x10, 0x76, 0xc6, 0xa7, 0x8b, 0x39, 0x43, 0xe1, 0x3a, 0xb5, 0x56, 0x2a, 0xc0, 0x6d, 0xb3, 0x05, 0x22,
    0x66, 0xbf, 0xdc, 0x0b, 0xfa, 0x62, 0x48, 0xdd, 0x20, 0x11, 0x06, 0x36, 0xc9, 0xc1, 0xcf, 0xf6, 0x27, 0x52, 0xbb,
    0x69, 0xf5, 0xd4, 0x87, 0x7f, 0x84, 0x4c, 0xd2, 0x9c, 0x57, 0xa4, 0xbc, 0x4f, 0x9a, 0xdf, 0xfe, 0xd6, 0x8d, 0x7a,
    0xeb, 0x2b, 0x53, 0xd8, 0x5c, 0xa1, 0x14, 0x17, 0xfb, 0x23, 0xd5, 0x7d, 0x30, 0x67, 0x73, 0x08, 0x09, 0xee, 0xb7,
    0x70, 0x3f, 0x61, 0xb2, 0x19, 0x8e, 0x4e, 0xe5, 0x4b, 0x93, 0x8f, 0x5d, 0xdb, 0xa9, 0xad, 0xf1, 0xae, 0x2e, 0xcb,
    0x0d, 0xfc, 0xf4, 0x2d, 0x46, 0x6e, 0x1d, 0x97, 0xe8, 0xd1, 0xe9, 0x4d, 0x37, 0xa5, 0x75, 0x5e, 0x83, 0x9e, 0xab,
    0x82, 0x9d, 0xb9, 0x1c, 0xe0, 0xcd, 0x49, 0x89, 0x01, 0xb6, 0xbd, 0x58, 0x24, 0xa2, 0x5f, 0x38, 0x78, 0x99, 0x15,
    0x90, 0x50, 0xb8, 0x95, 0xe4, 0xd0, 0x91, 0xc7, 0xce, 0xed, 0x0f, 0xb4, 0x6f, 0xa0, 0xcc, 0xf0, 0x02, 0x4a, 0x79,
    0xc3, 0xde, 0xa3, 0xef, 0xea, 0x51, 0xe6, 0x6b, 0x18, 0xec, 0x1b, 0x2c, 0x80, 0xf7, 0x74, 0xe7, 0xff, 0x21, 0x5a,
    0x6a, 0x54, 0x1e, 0x41, 0x31, 0x92, 0x35, 0xc4, 0x33, 0x07, 0x0a, 0xba, 0x7e, 0x0e, 0x34, 0x88, 0xb1, 0x98, 0x7c,
    0xf3, 0x3d, 0x60, 0x6c, 0x7b, 0xca, 0xd3, 0x1f, 0x32, 0x65, 0x04, 0x28, 0x64, 0xbe, 0x85, 0x9b, 0x2f, 0x59, 0x8a,
    0xd7, 0xb0, 0x25, 0xac, 0xaf, 0x12, 0x03, 0xe2, 0xf2};

static thread_local uint32_t EK_d[16] = {0x44D7, 0x26BC, 0x626B, 0x135E, 0x5789, 0x35E2, 0x7135, 0x09AF,
                                         0x4D78, 0x2F13, 0x6BC4, 0x1AF1, 0x5E26, 0x3C4D, 0x789A, 0x47AC};

static uint32_t AddM(uint32_t a, uint32_t b)
{
    uint32_t c = a + b;
    return (c & 0x7FFFFFFF) + (c >> 31);
}

#define MulByPow2(x, k) ((((x) << k) | ((x) >> (31 - k))) & 0x7FFFFFFF)

static void LFSRWithInitializationMode(uint32_t u)
{
    uint32_t f, v;

    f = LFSR_S[0];
    v = MulByPow2(LFSR_S[0], 8);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[4], 20);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[10], 21);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[13], 17);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[15], 15);
    f = AddM(f, v);

    f = AddM(f, u);

    for (int i = 0; i < 15; ++i)
        LFSR_S[i] = LFSR_S[i + 1];
    LFSR_S[15] = f;
}

static void LFSRWithWorkMode()
{
    uint32_t f, v;

    f = LFSR_S[0];
    v = MulByPow2(LFSR_S[0], 8);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[4], 20);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[10], 21);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[13], 17);
    f = AddM(f, v);

    v = MulByPow2(LFSR_S[15], 15);
    f = AddM(f, v);

    for (int i = 0; i < 15; ++i)
        LFSR_S[i] = LFSR_S[i + 1];
    LFSR_S[15] = f;
}

static void BitReorganization()
{
    BRC_X[0] = ((LFSR_S[15] & 0x7FFF8000) << 1) | (LFSR_S[14] & 0xFFFF);
    BRC_X[1] = ((LFSR_S[11] & 0xFFFF) << 16) | (LFSR_S[9] >> 15);
    BRC_X[2] = ((LFSR_S[7] & 0xFFFF) << 16) | (LFSR_S[5] >> 15);
    BRC_X[3] = ((LFSR_S[2] & 0xFFFF) << 16) | (LFSR_S[0] >> 15);
}

#define ROT(a, k) (((a) << k) | ((a) >> (32 - k)))

static uint32_t L1(uint32_t X)
{
    return (X ^ ROT(X, 2) ^ ROT(X, 10) ^ ROT(X, 18) ^ ROT(X, 24));
}

static uint32_t L2(uint32_t X)
{
    return (X ^ ROT(X, 8) ^ ROT(X, 14) ^ ROT(X, 22) ^ ROT(X, 30));
}

#define MAKEU32(a, b, c, d) (((uint32_t)(a) << 24) | ((uint32_t)(b) << 16) | ((uint32_t)(c) << 8) | ((uint32_t)(d)))

static uint32_t F()
{
    uint32_t W, W1, W2, u, v;

    W = (BRC_X[0] ^ F_R1) + F_R2;
    W1 = F_R1 + BRC_X[1];
    W2 = F_R2 ^ BRC_X[2];
    u = L1((W1 << 16) | (W2 >> 16));
    v = L2((W2 << 16) | (W1 >> 16));
    F_R1 = MAKEU32(S0[u >> 24], S1[(u >> 16) & 0xFF], S0[(u >> 8) & 0xFF], S1[u & 0xFF]);
    F_R2 = MAKEU32(S0[v >> 24], S1[(v >> 16) & 0xFF], S0[(v >> 8) & 0xFF], S1[v & 0xFF]);

    return W;
}

#define MAKEU31(a, b, c)                                                                                               \
    (((uint32_t)((uint32_t)(0) | (uint8_t)(a)) << 23) | ((uint32_t)(b) << 8) | (uint32_t)((uint32_t)(0) | (uint8_t)(c)))

void crypto::zuc::Initialize(const uint8_t *pKey, const uint8_t *pIv)
{
    uint32_t w;

    for (int i = 0; i < 16; ++i)
        LFSR_S[i] = MAKEU31(pKey[i], EK_d[i], pIv[i]);

    F_R1 = 0;
    F_R2 = 0;
    uint32_t nCount = 32;
    while (nCount > 0)
    {
        BitReorganization();
        w = F();
        LFSRWithInitializationMode(w >> 1);
        nCount--;
    }

    BitReorganization();
    F();
    LFSRWithWorkMode();
}

void crypto::zuc::GenerateKeyStream(uint32_t *pKeyStream, uint32_t nKeyStream)
{
    for (uint32_t i = 0; i < nKeyStream; ++i)
    {
        BitReorganization();
        pKeyStream[i] = F() ^ BRC_X[3];
        LFSRWithWorkMode();
    }
}